In a reciprocating type internal combustion engine or compressor, a conversion between a reciprocating motion of a piston and a rotary motion of a crankshaft is required to be realized, wherein the reciprocating motion of the piston is converted into the rotary motion of the crankshaft in the reciprocating type internal combustion engine, while the rotary motion of the crankshaft is converted into the reciprocating motion of the piston in the reciprocating type compressor. In current known technologies, the above-described conversion requires the use of a crank-link mechanism. The machine becomes bulky and heavy due to the existence of links in the crank-link mechanism, making it impossible to a complete balance.
In order to solve the above discussed problem, Chinese patent CN85100359A discloses a “reciprocating piston type internal combustion engine with crank-dual circular slide block”, Chinese patent ZL95111404.2 protects a “reciprocating piston type internal combustion engine with crank-dual circular slide block”, and Chinese patent ZL95111403.4 protects a “reciprocating piston type internal combustion engine with crank-multiple circular slide block”. A common feature of the above internal combustion engines is that a thorough improvement is made on the crank-link mechanism of internal combustion engine in known technologies, by use of substituting the link with a circular slide block having an eccentric circular hole. The eccentric circular slide block is of a cylinder shape and is provided with an eccentric circular hole which is in parallel with the axis of the cylinder and passed through by a crank pin of the crankshaft. A piston of the internal combustion engine includes crown portions at both ends thereof and a guide portion connecting the crown portions, wherein the guide portion is provided with a circular hole thereon whose inside diameter surface matches with an outside diameter surface of the circular slide block so that the circular slide block is placed into the circular hole of the guide portion of the piston which matches with the outer periphery of the circular slide block. When the piston reciprocates in the cylinder under the push of combusted gas in the cylinder, the eccentric circular slide block rotates about its own center of circle and further drives the crankshaft to rotate in an opposite direction, so that the reciprocating motion of the piston is converted into the rotary motion of the crankshaft and then power is transmitted outwardly by rotating parts connected to the crankshaft. The ideas of the above patents can also be conveniently applied to a compressor to obtain a crank circular slide block compressor.
In the above discussed crank circular slide block type internal combustion engine or compressor, the crankshaft remains to be an indispensable part. The crankshaft has a main journal and a crank pin, wherein the main journal is used for supporting the crankshaft on the cylinder body by means of a bearing, and the crank pin passes through the eccentric circular hole of the circular slide block. Since the diameter of the main journal is larger than that of the crank pin, the main journal at both ends will necessarily completely enclose the left and right sides of the axis of the crank pin. Therefore, the problem with how to fit the circular slide block over the crank pin must be taken into consideration.
One of the ways to solve the above problem is to design the circular slide block as a split structure, i.e., the circular slide block is divided into two halves: a left part and a right part that are semi-circle respectively. Upon installation, the left part and the right part fit over the crank pin by facing them each other, and then bringing the two parts into an integral part by means of a lock-up structure. Although this method can solve the above problem, the circular slide block itself is small in size and the eccentric circular hole is also required to be provided, making the space for arranging the lock up structure limited. Besides, the circular slide block is subject to a very large force when the engine is in operation, therefore the lock up structure tends to fail. Therefore, this kind of circular slide block having split structure is not an optimum solution.